I will be traveling from Rome to Florence on 3/21, which is a date where I now know there is a planned rail strike. I looked at the government site, but I could not tell how the strike would affect my trip. It is the Trenitalia high speed train. How worried should I be about this?
High speed trains are usually not affected by strikes. You should be there a little earlier. Depending on the operational situation, trains sometimes leave earlier.
I would not. Strikes are frequently "discussed" but seldom enacted. And if they are, not all trains are effected. There are always few trains running. Be flexible and you will be OK.
It looks to me like there are a bunch of strikes listed for 3/21 but they are all shown as "local transport" so your train should be fine. However, in my limited experience, while some announced strikes don't materialize, others spread to more sectors or regions a day or 2 before. If you are concerned, check with a tourist information office a day or so ahead while you are in Rome where they should be able to give you more specific information. You can also check the Trenitalia website closer to the date. On most routes, there are usually at least a couple guaranteed trains, usually during morning and evening communter hours, that will run. You can find a list somewhere online (I can't remember where). Worst case, you could look at an Italo train (less likely affected) or bus.
No worries. If you were going on the 19th Trenitalia high speed trains are affected, but not on the 21st if you trust the Google translation of the page
On March 21, 2025, a 24-hour strike was called by the staff of companies to which the National Collective Labor Agreement of Autoferrotranvieri applies. Trenitalia Frecciarossa, Frecciargento, Frecciabianca, Intercity, Intercity Notte, EuroCity, EuroNight and Regional trains are running regularly.
https://www.trenitalia.com/it/informazioni/treni_garantiti_incasodisciopero.html